云贵彝良-威宁中强地震地震动特性

2012年9月7日，我国西南云贵交界彝良-威宁地区连续发生两次中强地震，为地震动特性的比较研究提供了强震动记录．考虑距离、方向的影响，从地震动衰减关系和反应谱两个方面考查了两次地震强震动的工程特征．结果显示，竖向地震动峰值在近场和中场区域明显高于水平向地震动，竖向地震动峰值随距离衰减更快；55．6级地震动峰值在近场和中场明显大于必；5．7级地震动，但地震动峰值衰减速度也较快；与其他研究结果比较表明，这两次地震的峰值总体上偏低．尽管两次地震绝大多数台站的场地为土层场地，但其平均规准谱在中长周期段的谱值明显低于规范设计谱．

Characteristics of Ground Motions of Yiliang-Weining Earthquakes in Yunnan and Guizhou

On September 7, 2012, two earthquakes with similar magnitude occurred at the boundary between Yun- Gui Yiliang-Weining counties, southwest of China, in which a number of valuable strong ground motion recordings were obtained. Ground motion attenuation relationships and response spectra were examined by considering the influ- ence of epicentral distance and component direction. Results show that, peak ground amplitudes of the vertical com- ponents are obviously larger than those of the horizontal components in the near- and middle-distant source regions, while they also attenuate faster than the horizontal motions; peak ground amplitudes of the M~5.6 earthquake are clearly larger than those of the Ms5.7 event in the near- and middle-distant source regions, but decrease faster with distance increasing; ground motion amplitudes are totally lower than those of the other studies; normalized spectra at medium and long periods are lower than those of code design spectra though most of the recording stations are from soil sites during two earthquakes.